The proposed research has three major objectives, all of which focus on delineating the patterning or structure of health-related behavior, including drug and alcohol use, in an adolescent sample. The first objective is to gain a clearer understanding of the relation of alcohol/drug use to other behaviors, and of the centrality of alcohol/drug use in a larger "syndrome" that includes smoking, problem drinking, delinquent behavior, and precocious sexual behavior. This syndrome of problem behavior will be studied to determine where the boundaries may fall, and whether other health-related behaviors such as physical exercise, risk-taking, eating behaviors and sleeping habits, and stress coping patterns are components in the same behavioral syndrome. This will involve examination of the interrelations among problem behaviors, between problem behaviors and other health-compromising behaviors, and between both of these categories and health-enhancing behaviors. The second main objective is to investigate the psychosocial mechanisms that could account for the observed covariation among the various behaviors within the syndrome. The focus here will include: a) examination of the similarity between the psychosocial correlates of alcohol/drug use and the psychosocial correlates of the various other behaviors; b) consideration of the similarity of the psychological functions of the correlated behaviors; c) study of the co-learning of the correlated behaviors; and d) determination of the naturalistic linkages among the correlated behaviors in the social ecology of adolescence. The third objective is to examine gender and age-related differences in the patterning and the structure of covariation of drug use with other health-related behavior across the adolescent years.